With the growth of world energy demand, alternative energy sources for satisfying such demand have prompted widespread research and development. One such promising alternative energy source is biofuel, which encompasses various types of combustible fuels that are derived from organic biomass. There is a strong desire to develop biofuels that are cost-competitive with fossil fuels due to both environmental benefits as well as the renewable nature of biofuels. One particular type of biofuel is biomass-derived pyrolysis oil. Biomass-derived pyrolysis oil can be burned directly as fuel for certain boiler and furnace applications. Biomass-derived pyrolysis oil can also serve as a potential feedstock in catalytic processes for the production of fuel in petroleum refineries. Biomass-derived pyrolysis oil has the potential to replace up to 60% of transportation fuels, thereby reducing the dependency on conventional fossil fuel and reducing its environmental impact.
Biomass-derived pyrolysis oil is produced through pyrolysis, including through recently-developed fast pyrolysis processes. Fast pyrolysis is a process during which organic biomass, such as wood waste, agricultural waste, etc., are rapidly heated to about 450° C. to about 600° C. in the absence of air using a pyrolysis reactor. Under these conditions, a pyrolysis vapor stream including organic vapors, water vapor, and pyrolysis gases is produced, along with char (which includes ash and combustible hydrocarbon solids). A portion of the pyrolysis vapor stream is condensed in a quenching system to biomass-derived pyrolysis oil. The quenching system contains a primary condenser and, in some instances, a secondary condenser. When the primary and secondary condensers are used, the majority of the biomass-derived pyrolysis oil is yielded in the primary condenser and a minor amount of biomass-derived pyrolysis oil is yielded in the secondary condenser. Biomass-derived pyrolysis oil is a complex, highly oxygenated organic liquid typically containing about 20-30% by weight water with high acidity (TAN>150).
One factor that affects the yield of biomass-derived pyrolysis oil is the amount of ash that is present in the biomass, with high ash content in the biomass reducing the yield of biomass-derived pyrolysis oil. The ash is the solid portion of the biomass that remains after a sample of the biomass is combusted according to ASTM D482. The ash content of the biomass is dependent upon the amount of metals that are present in the biomass. For various types of biomass, such as food crops, fertilizers are used that contain metals such as potassium to promote fruit yield. Because certain food crops yield significant amounts of expended biomass (such as expended fruit bunches), the expended biomass may provide a commercially significant source of biomass-derived pyrolysis oil. However, while the fertilizers used on the food crops are desirable for promoting fruit yield, the metals from the fertilizers are incorporated into the biomass that is subject to pyrolysis and result in reduced yields as compared to crops that are not treated with fertilizers.
To increase liquid yield and reduce the ash content of the biomass, simple washing steps have been employed using water to remove water-soluble metals from the biomass. However, water can be scarce in various locations at which pyrolysis is conducted.
Accordingly, it is desirable to provide methods for forming a low-metal biomass-derived pyrolysis oil, as well as apparatuses for forming the low-metal biomass-derived pyrolysis oil, that minimize the need to secure an independent source of water. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.